Add README and Travis file
Add stuff for the Github mirror (README, Travis file and gitignore files).
// Copyright (C) 2016 Mikael Berthe <mikael@lilotux.net>. All rights reserved.
// Use of this source code is governed by the MIT license,
// which can be found in the LICENSE file.
package takuzu
// This file contains the methods used to solve a takuzu puzzle.
import (
"fmt"
"log"
"runtime"
"sync"
"time"
"github.com/pkg/errors"
)
var verbosity int
var schrodLvl uint
// SetVerbosityLevel initializes the verbosity level of the resolution
// routines.
func SetVerbosityLevel(level int) {
verbosity = level
}
// SetSchrodingerLevel initializes the "Schrödinger" level (0 means disabled)
// It must be called before any board generation or reduction.
func SetSchrodingerLevel(level uint) {
schrodLvl = level
}
func (b Takuzu) guessPos(l, c int) int {
if b.Board[l][c].Defined {
return b.Board[l][c].Value
}
bx := b.Clone()
bx.Set(l, c, 0)
bx.FillLineColumn(l, c)
if bx.CheckLine(l) != nil || bx.CheckColumn(c) != nil {
return 1
}
Copy(&b, &bx)
bx.Set(l, c, 1)
bx.FillLineColumn(l, c)
if bx.CheckLine(l) != nil || bx.CheckColumn(c) != nil {
return 0
}
return -1 // dunno
}
// TrivialHint returns the coordinates and the value of the first cell that
// can be guessed using trivial methods.
// It returns {-1, -1, -1} if none can be found.
func (b Takuzu) TrivialHint() (line, col, value int) {
for line = 0; line < b.Size; line++ {
for col = 0; col < b.Size; col++ {
if b.Board[line][col].Defined {
continue
}
if value = b.guessPos(line, col); value != -1 {
return
}
}
}
value, line, col = -1, -1, -1
return
}
// trySolveTrivialPass does 1 pass over the takuzu board and tries to find
// values using simple guesses.
func (b Takuzu) trySolveTrivialPass() (changed bool) {
for line := 0; line < b.Size; line++ {
for col := 0; col < b.Size; col++ {
if b.Board[line][col].Defined {
continue
}
if guess := b.guessPos(line, col); guess != -1 {
b.Set(line, col, guess)
if verbosity > 3 {
log.Printf("Trivial: Setting [%d,%d] to %d", line, col, guess)
}
changed = true // Ideally remember l,c
}
}
}
return changed
}
// TrySolveTrivial tries to solve the takuzu using a loop over simple methods
// It returns true if all cells are defined, and an error if the grid breaks the rules.
func (b Takuzu) TrySolveTrivial() (bool, error) {
for {
changed := b.trySolveTrivialPass()
if verbosity > 3 {
var status string
if changed {
status = "ongoing"
} else {
status = "stuck"
}
log.Println("Trivial resolution -", status)
}
if !changed {
break
}
if verbosity > 3 {
b.DumpBoard()
fmt.Println()
}
}
full, err := b.Validate()
if err != nil {
return full, errors.Wrap(err, "the takuzu looks wrong")
}
return full, nil
}
// TrySolveRecurse tries to solve the takuzu recursively, using trivial
// method first and using guesses if it fails.
func (b Takuzu) TrySolveRecurse(allSolutions *[]Takuzu, timeout time.Duration) (*Takuzu, error) {
var solutionsMux sync.Mutex
var singleSolution *Takuzu
var solutionMap map[string]*Takuzu
var globalSearch bool
// globalSearch doesn't need to use a mutex and is more convenient
// to use than allSolutions.
if allSolutions != nil {
globalSearch = true
solutionMap = make(map[string]*Takuzu)
}
startTime := time.Now()
var recurseSolve func(level int, t Takuzu, errStatus chan<- error) error
recurseSolve = func(level int, t Takuzu, errStatus chan<- error) error {
reportStatus := func(failure error) {
// Report status to the caller's channel
if errStatus != nil {
errStatus <- failure
}
}
// In Schröndinger mode we check concurrently both values for a cell
var schrodinger bool
concurrentRoutines := 1
if level < int(schrodLvl) {
schrodinger = true
concurrentRoutines = 2
}
var status [2]chan error
status[0] = make(chan error)
status[1] = make(chan error)
for {
// Try simple resolution first
full, err := t.TrySolveTrivial()
if err != nil {
reportStatus(err)
return err
}
if full { // We're done
if verbosity > 1 {
log.Printf("{%d} The takuzu is correct and complete.", level)
}
solutionsMux.Lock()
singleSolution = &t
if globalSearch {
solutionMap[t.ToString()] = &t
}
solutionsMux.Unlock()
reportStatus(nil)
return nil
}
if verbosity > 2 {
log.Printf("{%d} Trivial resolution did not complete.", level)
}
// Trivial method is stuck, let's use recursion
changed := false
// Looking for first empty cell
var line, col int
firstClear:
for line = 0; line < t.Size; line++ {
for col = 0; col < t.Size; col++ {
if !t.Board[line][col].Defined {
break firstClear
}
}
}
if line == t.Size || col == t.Size {
break
}
if verbosity > 2 {
log.Printf("{%d} GUESS - Trying values for [%d,%d]", level, line, col)
}
var val int
err = nil
errCount := 0
for testval := 0; testval < 2; testval++ {
if !globalSearch && t.Board[line][col].Defined {
// No need to "guess" here anymore
break
}
// Launch goroutines for cell values of 0 and/or 1
for testCase := 0; testCase < 2; testCase++ {
if schrodinger || testval == testCase {
tx := t.Clone()
tx.Set(line, col, testCase)
go recurseSolve(level+1, tx, status[testCase])
}
}
// Let's collect the goroutines' results
for i := 0; i < concurrentRoutines; i++ {
if schrodinger && verbosity > 1 { // XXX
log.Printf("{%d} Schrodinger waiting for result #%d for cell [%d,%d]", level, i, line, col)
}
select {
case e := <-status[0]:
err = e
val = 0
case e := <-status[1]:
err = e
val = 1
}
if schrodinger && verbosity > 1 { // XXX
log.Printf("{%d} Schrodinger result #%d/2 for cell [%d,%d]=%d - err=%v", level, i+1, line, col, val, err)
}
if err == nil {
if !globalSearch {
reportStatus(nil)
if i+1 < concurrentRoutines {
// Schröndinger mode and we still have one status to fetch
<-status[1-val]
}
return nil
}
continue
}
if timeout > 0 && level > 2 && time.Since(startTime) > timeout {
if errors.Cause(err).Error() != "timeout" {
if verbosity > 0 {
log.Printf("{%d} Timeout, giving up", level)
}
err := errors.New("timeout")
reportStatus(err)
if i+1 < concurrentRoutines {
// Schröndinger mode and we still have one status to fetch
<-status[1-val]
}
// XXX actually can't close the channel and leave, can I?
return err
}
}
// err != nil: we can set a value -- unless this was a timeout
if errors.Cause(err).Error() == "timeout" {
if verbosity > 1 {
log.Printf("{%d} Timeout propagation", level)
}
reportStatus(err)
if i+1 < concurrentRoutines {
// Schröndinger mode and we still have one status to fetch
<-status[1-val]
}
// XXX actually can't close the channel and leave, can I?
return err
}
errCount++
if verbosity > 2 {
log.Printf("{%d} Bad outcome (%v)", level, err)
log.Printf("{%d} GUESS was wrong - Setting [%d,%d] to %d",
level, line, col, 1-val)
}
t.Set(line, col, 1-val)
changed = true
} // concurrentRoutines
if (changed && !globalSearch) || schrodinger {
// Let's loop again with the new board
break
}
}
if verbosity > 2 {
log.Printf("{%d} End of cycle.\n\n", level)
}
if errCount == 2 {
// Both values failed
err := errors.New("dead end")
reportStatus(err)
return err
}
// If we cannot fill more cells (!changed) or if we've made a global search with
// both values, the search is complete.
if schrodinger || globalSearch || !changed {
break
}
if verbosity > 2 {
t.DumpBoard()
fmt.Println()
}
}
// Try to force garbage collection
runtime.GC()
full, err := t.Validate()
if err != nil {
if verbosity > 1 {
log.Println("The takuzu looks wrong - ", err)
}
err := errors.Wrap(err, "the takuzu looks wrong")
reportStatus(err)
return err
}
if full {
if verbosity > 1 {
log.Println("The takuzu is correct and complete")
}
solutionsMux.Lock()
singleSolution = &t
if globalSearch {
solutionMap[t.ToString()] = &t
}
solutionsMux.Unlock()
}
reportStatus(nil)
return nil
}
status := make(chan error)
go recurseSolve(0, b, status)
err := <-status // Wait for it...
firstSol := singleSolution
if globalSearch {
for _, tp := range solutionMap {
*allSolutions = append(*allSolutions, *tp)
}
}
if err != nil {
return firstSol, err
}
if globalSearch && len(*allSolutions) > 0 {
firstSol = &(*allSolutions)[0]
}
return firstSol, nil
}